Backblaze is not the government. I mean if you're paranoid about it you could submit a bug bounty with a temporary email address and gauge the response. If I were Backblaze I would like to know about this and would be willing to at least send you a pair of new replacement drives to get that one back, assuming this kind of disposal is not their SOP. It's possible they ran this drive through their vetting process and it didn't meet their spec so they sold it off. The logs might just be from that testing/vetting and any data even on real production backblaze drives I would assume is so striped-out that a single disk would not have anything of recoverable value.